There is known a vehicle body front structure in which the front fastening portions and the rear fastening portions of a sub frame are connected from below to front side frames, a front bulkhead is provided on the front portions of the front side frames, and the lower end of the front bulkhead and the front end of the sub frame are connected by an extended arm (for example, see PTL 1).
According to this vehicle body front structure, when an impact load is input to the lower portion of the front bulkhead by a front collision, the vicinity of the connecting portion between the extended arm and the sub frame bends downward. When the vicinity of the connecting portion bends downward, the sub frame starts rotating downward using the rear end of the sub frame as a fulcrum, and the front fastening portions of the sub frame separate from the front side frames.
Here, the rear fastening portions are provided on the front side of the rear end of the sub frame in the vehicle body. Hence, when the sub frame rotates downward using the rear end as a fulcrum, the rear fastening portions of the sub frame are separated from the front side frames.
The sub frame is thus separated from the front side frames, and it is therefore possible to ensure the deformation amount of the front side frames and absorb impact energy input by the front collision.
In the vehicle body front structure of PTL 1, however, the sub frame is rotated downward only by the extended arm that connects the lower end of the front bulkhead and the front end of the sub frame. Hence, to further increase the impact energy absorbing amount, a contrivance to further ensure the deformation amount of the front side frames is needed.
There is also known a vehicle body front structure in which front side frames are deformed by a front collision, thereby separating the front fastening portions and the rear fastening portions of a sub frame and thus separating the sub frame from the front side frames. It is therefore possible to ensure the deformation amount of the front side frames and absorb impact energy input by the front collision (for example, see PTL 2).
In the vehicle body front structure of PTL 2, however, the front fastening portions and the rear fastening portions of the sub frame need to be separated from the front side frames only by the deformation of the front side frames. Hence, it is difficult to reliably separate the sub frame from the front side frames.
For this reason, the sub frame remains unseparated from the front side frames, and the sub frame becomes an obstruction. It is difficult to sufficiently ensure the deformation amount of the front side frames and increase the impact energy absorbing amount.
There is also known a vehicle body front structure in which a power train is bumped against the catcher bracket of a sub frame by a front collision, an impact load is input to the catcher bracket horizontally toward the rear of the vehicle body, and the rear fastening portions of the sub frame are separated from the front side frames by the input impact load only by a shearing load (for example, see PTL 3).
However, it is difficult to separate the rear fastening portions of the sub frame from the front side frames only by the shearing load, as in the vehicle body front structure of PTL 3.
For this reason, the sub frame remains unseparated from the front side frames, and the sub frame becomes an obstruction. It is difficult to sufficiently ensure the deformation amount of the front side frames and increase the impact energy absorbing amount.